One of the awkward problems you can encounter with parallel execution is data skew – which has the potential to make just one slave in a set do (almost) all the work hence reducing the performance to something close to serial execution times. has written a series of articles on Parallel Skew that has been published by AllthingsOracle over the last few months.

[…] operation, which means they can report the wrong order. [Update 3/Jan/2015: Here’s a link to a catalogue of articles that Randolf Geist and I have written about parallel execution plans showing (a.o.) the failure of […]